Propellant comprising a perfluoroguanidine containing oxidant and a fuel



United States Patent 3,354,011 PROPELLANT COMPRISING A PERFLUORO-GUANIDINE CONTAINING OXIDANT AND A FUEL James L. Kroon and Ralph A.Davis, Midland, Mich., as-

signors to The Dow Chemical Company, Midland, Mich., a corporation ofDelaware No Drawing. Original application July 14, 1961, Ser. No.126,441. Divided and this application Mar. 29, 1963, Ser. No. 270,490

1 Claim. (Cl. 149-22) This application is a division of our copendingapplication Ser. No. 126,441, filed July 14, 1961. This inventionpertains to a substituted guanidine, more particularlyperfluoroguanidine and its use in a propellant composition.

The novel perfluoroguanidine is a clear colorless liquid having aboiling point of 1.1 C. and a formula:

The novel compound finds utility as an intermediate and as an oxidantfor fuels in propellants. For the most efficient use ofperfluoroguanidine as an oxidant, perfluoroguanidine is generallyintermixed with an oxygen containing oxidant in an amount suflicient tooxidize the carbon in the perfluoroguanidine and the fuel. Examples ofsome of the commonly used oxygen containing oxidants which may beintermixed with the perfluoroguanidine for this purpose areperchlorates, nitrates, N 0 and other nitro compounds such astetranitromethane. When perfluoroguanidine is used as an oxidant with N0, for a fuel, such as pentaborane, a theoretical specific impulse of325 is obtained. It may be used very conveniently with liquid propellantfuels, such as hydrazine and substituted hydrazines. When it is usedwith hydrazine and a mixture of N 0 a theoretical specific impulse of307 is obtained. It may also be used with solid fuels, such as lithium,aluminum, beryllium, and the hydrides of these metals.

The new compound may be prepared by the fluorination of guanidine in thepresence of an alkali metal fluoride, alkaline earth metal fluoride, oran oxide of alkaline earth metals, aluminum, vanadium, titanium, andzirconium as described in patent application Ser. No. 63,215 dated Oct.17, 1960, now US. Patent No. 3,228,936, of Ralph A. Davis, coinventor inthe instant application, and one Kenneth O. Groves.

In carrying out the reaction, guanidine as a hydrofluoric acid salt or asalt of a mineral acid is intermixed with the particular metal fluorideor oxide and the mixture contacted with fluorine gas generally dilutedwith an inert diluent. Various known methods and equipment for carryingout the gas-solid reactions may be used. A fixed or fluidized bedreactor is often the most convenient method.

Although the weight ratio of the metal fluoride or oxide to guanidineused may be as little as 0.5 :1, it may be as high as 10:1. It isgenerally preferred to use an amount of the metal fluoride or oxidewhich is from 2 to 5 times that of the guanidine.

Any inert gaseous diluent may be intermixed with fluorine used in thefiuorination. Nitrogen is most conveniently used due to itsavailability. The fluorine concentration in the gaseous mixture isgenerally in the range of 1 to 30 volume percent. With a concentrationbelow 1 volume percent of fluorine, the reaction rate is too slow forpractical use but operative. A gas mixture containing over 50 volumepercent of fluorine is seldom employed.

While temperatures below -20 C. may be used for carrying out thereaction, the reaction is preferably carried out at about 0 C. Theperfluoroguanidine formed is thus vaporized and recovered in a condensermaintained at a temperature below the boiling point of theperfluoroguanidine. The product thus obtained by condensation may befurther purified if desired by further distillation.

To illustrate the preparation of perfluoroguanidine, 24 grams ofmagnesium fluoride and 24 grams of sodium fluoride were placed in athree necked Monel flask equipped with a stirrer. Five grams ofguanidine hydrofluoride were added to the Monel flask and the flask wasflushed with nitrogen gas. The flow of nitrogen gas was adjusted to 300milliliters per minute. The flask was then immersed in Wet ice andfluorine introduced into the flask at a rate of 100 milliliters perminute while the contents were being stirred. Fluorination was allowedto proceed for approximately two hours with constant stirring. Thevapors from the Monel flask were passed through a trap maintained at C.with solid carbon dioxide.

The perfluoroguanidine thus obtained and further purified bydistillation had a boiling point of -1.1 C. and was a colorless liquid.Three molecular weight measurements were made using the vapor-densitymethod. It was found that the molecular weight was 149.0, 148.4 and148.1. The formula weight of perfluoroguanidine is 149.0.

The Antoine equation constants were found to be, A=6.2385; B=689.385;and C=206.44. The heat of vaporization at 1.1 C. was 5.5 kilocaloriesper mole.

Infrared spectrum showed a large NF absorption in the 10-11 micronregion, the absence of a CF absorption in the 7-8 micron region, and aweak but definite absorption peak of the C=N bond at 6.1-6.2 microns.Mass spectrometry data indicated mass peaks at 149, 97, 78 and 5 9,confirming molecular weight measurements. The magnetic resonance dataindicated the presence of two NF groups and one C=NF group.

What is claimed is:

In a propellant containing an oxidant and a fuel, said oxidantconsisting essentially of a mixture of perfluoroguanidine and an oxygencontaining oxidant selected from the group consisting essentially ofperchlorates, nitrates, nitrogen tetroxide and tetranitromethane andsaid fuel being a member selected from the group consisting essentiallyof tetraborane, hydrazine, lithium, aluminum, beryl lium and hydrides ofthese metals, the amount of said oxidant being suflicient to oxidize thecarbon in said perfiuoroguanidine and said fuel member.

No references cited.

CARL D. QUARFORTH, Primary Examiner.

L. A. SEBASTIAN, Assistant Examiner.

